In recent years, greater attention has been paid to how businesses are addressing the issues of global warming. There is a greater possibility that companies will set a CO2 emissions reduction target as a management indicator, as well as other possibilities. In this manner, the public interest in how to pay attention to the environment is growing. However, as IT (Information Technology) devices and other devices improve in performance, the IT devices tend to consume much more power. Therefore, there is a pressing need to curb the power consumption of the IT devices.
By the way, in a conventional power supply device, a heavy load comes with high power conversion efficiency, and a light load with low power conversion efficiency. Therefore, a heavy load is not always applied on the power supply device. For example, the problem is that the power loss caused by a power supply device increases in a server or the like where a load is light for a long period of time.
For example, the following is disclosed in PTL1: An AC/DC converter is made small and lightweight by covering a part of the peak-time power with a supply from a secondary battery, and, when the power consumption of a load is small, power is supplied from the secondary battery to the load after the AC/DC converter is stopped
The following is disclosed in PTL 2: In an electric device to which a power supply unit such as an AC adapter is connected, with the AC adapter being connected to a system, power is supplied from a battery to the system when the system is switched off or when a load is light.
The following is disclosed in PTL 3: Power is accumulated in a charging unit when the efficiency of a switching power supply (PSU: Power Supply Unit) is high, and, when the efficiency of the PSU is low, power is supplied to a load with the use of the power accumulated in the charging unit.
The following is disclosed in PTL 4: When the remaining capacity of an electric storage device is less than or equal to a predetermined value, a load switches from supplying power to an electronics device to supplying power to a power supply device, and a current supplied from the power supply device is controlled to charge a charging device so that the conversion efficiency of the power supply device is at the highest level.
The following is disclosed in PTL 5: When in operation, an electronics system calculates the power consumption of the electronics system with the use of a direct current generated from an alternating-current power supply, and, when the electronics system starts to operate with the use of the power from a battery, the connection time of the battery is calculated based on the amount of remaining charge in the battery and the value of the power consumption.